libwebsockets v2.3 released 2017-07-28

v2.3 adds many fixes and features, including the new "lws-meta" multiplexing protocol. See the changelog link above for details.

libwebsockets v2.2 released 2017-03-08

v2.2 adds support for ESP32 ^^, serving gzipped-compressed files directly from inside a zip, raw file and socket integration, full RFC7233 RANGES support, Basic Auth security per-mount, and many more new features and improvements. See the changelog link above for more details.

libwebsockets v2.1 released 2016-10-06

Building on v2.0, v2.1 adds many new features to lwsws and new plugins, as well as new API support like multipart formas and file upload. The documentation has been reworked using Doxygen.
ESP8266 is also supported ^^
See the changelog above for more info.

LWSWS standalone webserver (used by this site) lets you configure lws features by JSON and avoid writing any code

libwebsockets features

Provides server and client APIs for RFC6455 v13 ws:// and wss:// websocket protocol, along with http:// and https://

Can be configured to use OpenSSL, CyaSSL, WolfSSL, BoringSSL and mbedTLS to provide fully encrypted
client and server links - including client certificate support

HTTP/2 server support integrated on same listen port as http/1 and ws[s], ALPN supported

Lightweight and fast even at 250K connections per thread and beyond - performance per byte and performance per MIPS many times better than traditional solutions

CMake based project that has been used in a variety of OS contexts including Linux
(uclibc and glibc), ARM-based embedded boards, OP-TEE, MIPS / OpenWRT, Windows, Android,
Apple iOS and even Tivo. It's used all over the place including The New York Times
customer-facing servers and BMW.

It includes a stub webserver that is enough to deliver your scripts to the browser that
open websocket connections back to the same server, so it can solve the entire server side,
ws://, wss://, http://, and https:// in one step.
Apache, Java or any other server-side support is not needed.

Compliant browsers from the last few years are supported on any platform.